More specifically, the invention concerns a machine for the continuous manufacture of creped paper wherein following formation, draining and any partial drying, the web is applied against a suitably heated drying cylinder. Following drying, the web is detached from the cylinder by a creping blade scraping the cylinder surface at an appropriate angle. Thus detached and creped, the web is longitudinally moved to a rewinder.
Furthermore, cellulose wadding or tissue paper for domestic or sanitary uses, for example toilet paper, paper towels, handkerchiefs, napkins, and the like, are manufactured in the above manner.
By scraping the cylinder, the creping blade detaches the web and forms crepe lines. The blade also tears off dust and paper fiber particles in varying degrees depending on the pulp grade, the web's dryness, and any added loosening agents used to improve softness. A portion of the dust and fibers will tend to follow the paper path and the paper on account of the paper's high speed dragging along an air layer at each of its two sides. This moving air mass carries much dust.
However, even larger quantities of dust or larger fiber accumulations may be produced in the vicinity of the creping blade in a zone present between the detached paper web and the cylinder below the two surfaces.
Accordingly, dust so created is likely to accumulate on the paper-producing equipment and within the building housing the equipment. The dust creates a disadvantageous environment for workers around the equipment or in the building.
Moreover, the dust and torn-off fibers are highly flammable and susceptible to the least spark, in particular, between the creping blade and the drying cylinder, or in any other region of the equipment or building wherein they accumulate.
Generally, a drying cylinder is fitted with a drying hood representing another ignition source of dust accumulating on the equipment.
Lastly, these undesirable fiber particles may hamper proper operation of the equipment or they may degrade the final paper quality.
To confine dust dispersion, it has already been suggested to confine the equipment per se to preclude the dust from dispersing into the entire building. Hoods have been mounted on the machine parts between the heating cylinder and the rewinder as well as on the reel itself. Suction boxes producing advantageous air circulation are present inside these enclosures. These means are fairly effective to prevent dust from reaching the machine room and in restricting the danger of fire. However, the accumulation of dust and torn-off fibers on the machine per se remains a big unsolved problem.
Obviously dust accumulation is especially significant in the vicinity and just below the creping blade.
U.S. Pat. No. 5,011,574 already has proposed a creped paper making machine fitted with a suction dust control of which the air intakes are present in the immediate vicinity of the creping blade.
Another patent document, namely EP-A-0 310 161, discloses apparatus to aspirate dust in the air layer moving along the paper path.
U.S. Pat. No. 5,466,298 describes dust control apparatus for a paper web wherein compressed air is blown in very near one of the paper web sides to oppose the air flow following the paper path. By being mixed with the compressed air, the air mass is stopped and then aspirated by an adjacent suction device.
While the above techniques taken together allow reducing the dust generated at the facility or accumulating on the machine, they also require processing very large air masses and entail dust removal. The control of the above boxes is very difficult and they are easily clogged by dust or fiber aggregations. Moreover, being localized applications, they do not solve the overall problem of dust generation from the paper creping operation.